Geodesic enclosures are partially spherical lattice shell structures constructed of interlocking polygons. The completed shell structure of a geodesic enclosure can be covered externally or internally (or both) to create a partially spherical enclosure. Although originally used in architecture by the German engineer Walter Bauersfeld, Buckminster Fuller provided the mathematics, modern research and writings to promote and popularize the geodesic enclosure as an enclosure for humans. There are numerous uses for geodesic enclosures such as habitations for extreme environments; temporary enclosures during research, disaster, or humanitarian relief; as storage units for large objects; and, for events requiring an enclosed structure with a large volume capacity. It is well known in the art that geodesic enclosures can also provide notable stiffness and rigidity without the need for internal structural supports when the structure is assembled. Assembly of a geodesic enclosure can quickly become complex when dome components are not easily interchangeable as well as require different angles and multiple configurations. These difficulties can make assembly of a geodesic enclosure resource and time intensive.
The first known geodesic enclosure structure used in architecture was completed in 1923. Engineer Walther Bauersfeld first used the dome design for the planetarium in Jena, Germany to test his projector invention. Bauersfeld conceived of the dome so that he could display his recreation of the stars at the planetarium via his projector. For the projector of the stars to properly display the night sky, Bauerseld required a hemispheric dome. Bauersfeld improved his geodesic design over time, but the geodesic enclosure as a functional design for habitation and more was virtually ignored until Buckminster Fuller began publishing his materials.
A geodesic enclosure can provide the infrastructure for a habitat designed for isolated areas of the world, space exploration purposes, and for a myriad of other uses. Spherical designs provide the most volume within an enclosure while requiring the least surface area. Because geodesic enclosures have a high strength-to-weight ratio they may be a preferable habitation or storage structure for areas having harsh environmental conditions such as Antarctica, the ocean, space, or desert regions. In earthquake prone areas, the low center of gravity attributable to the geodesic enclosure design makes them more resistant to the effects of earthquakes than enclosures with a higher center of gravity. The U.S. military has already experimented with—as well as implemented—modular and portable geodesic enclosures for geographically isolated areas of the world for research and intelligence purposes.
One method of geodesic enclosure construction utilizes a series of hubs and struts that interconnect into a series of polygons to create the frame of a spherical structure, an aspherical structure, or any portion thereof. The number of hubs and struts needed for a geodesic enclosure as well as the angles that they would need to be placed at differ based on the size and frequency of the intended structure. The strut lengths also vary based on the desired size and frequency of a geodesic enclosure. However, larger geodesic enclosure structures require a higher frequency, which results in improved structural strength and stability compared to that of lower frequency domes.
Although geodesic enclosure designs are considered promising as a matter of architecture and habitation, there are design areas in which they can be noticeably improved upon. The strut ends in some current geodesic enclosure designs are often crimped so that they can be attached to a bolt, rivet, or other connecting means, reducing the overall strength of the strut. One problem with this prior art design is that the struts used to provide the frame currently offer minimal strength when connected at corresponding vertices in geodesic enclosure structures.
Moreover, different sizes and different frequencies of geodesic enclosures also require specific hubs and strut lengths to be precisely manufactured, which further increases manufacturing costs. Based on the frequency and size of the geodesic enclosure structure intended, specific hubs must be manufactured to conform to the various angles that the frequency requires. Struts for geodesic enclosures in the prior art are often cut as a matter of practice to their desired lengths, the ends are crimped and then a hole is drilled into the crimped end; a single bolt then secures the struts at a vertex. Crimping the strut component weakens its integrity and structural strength hence reducing the total load bearing capability of the dome. It would be advantageous if crimping of a strut could be eliminated and a modular approach applied to the manufacturing of structural components. There does not appear to be a universal hub and strut apparatus that exists that can be applied to all geodesic enclosure sizes and frequencies. It would be beneficial to have a modular dome assembly system with easily customizable hubs that could be quickly adapted to any geodesic enclosure size and frequency.
U.S. Pat. No. 4,357,118 to Murray discloses a hexagonal shaped connecting assembly for a geodesic enclosure. The connecting hub disclosed by Murray includes a plurality of U-shaped connecting members and U-shaped ports along the edges of the hexagonal shaped connecting assembly hub. The components are then connected via a bracket that is secured to both the hub and the strut. There are several limitations to this device compared to the present invention; for example, the device to Murray is not an assembly that would be universally compatible with multiple dome frequencies, which is important for reducing manufacturing and assembling costs for geodesic enclosure structures.
U.S. Pat. No. 4,262,461 to Johnson & Johnson discloses a geodesic enclosure connector. The connector interconnects the dome struts via a plurality of circumferentially spaced openings with a plurality of metal tongues that secure to the strut ends used for the dome. The strut ends connect into the spaced openings along the connector through one or more tapered pins used to secure the components.
U.S. Pat. No. 4,370,073 to Ohme discloses a connector hub for geodesic enclosure structures similar to the device claimed by Murray. As struts converge to the U-shaped connection points on the connector hub, the struts attach via hinge plates and connectors at the edges of each strut. The Ohme patent provides for an integrally cast connector hub with radially extending stringer receiving slots for struts used to assemble the dome structure. However, the Ohme hub fails to be universally applicable to all geodesic enclosure sizes and frequencies, which increases the manufacturing costs of dome structures using this hub design compared to that of the invention disclosed in the present application.
U.S. Pat. No. 4,844,649 to Vandenboom discloses a bracket assembly to interconnect support struts to create a dome structure. The apparatus claimed by Vandenboom allows for an adjustable way to connect struts in a geodesic enclosure design via an improved hub having bracket members that secure the struts to the claimed hub. However, the adjustability of the struts is a weakness in the Vandenboom patent that makes the Vandenboom dome structure less capable of bearing weight and pressure compared to similar structures built using the invention claimed herein.
U.S. Pat. No. 4,521,998 to DeLorme also discloses a hub connector for a geodesic enclosure. As struts converge, the struts attach via hinge plates and connectors at the edges of each strut. The advantage to the patent to DeLorme over the prior art is that the struts can be arranged in a number of combinations to create geodesic enclosures with unique triangle patterns, converging angles, articulating angles, and chord or strut lengths. However, the invention does not provide a universal system applicable to any frequency geodesic enclosure that also improves the strength of the assembled dome structure compared to that of the present invention.
U.S. Patent Application US/2006/0291952 to Wood describes a structural member connector for connecting a plurality of struts to one or more hubs on a geodesic enclosure or other design. An advantage to Wood's hub device is that the corresponding struts do not have to be flattened to attach to the strut. Although Wood's hub eliminates the need to flatten strut members, multiple hub configurations must still be designed based on the size and frequency of the dome.
U.S. Patent Application US/2009/0056239 to Wolfram discloses a hexagonal shaped connector for geodesic enclosure structures wherein each hexagonal edge includes strut portions that allow the actual strut component to be fastened to the connector. However, the struts used in the application to Wolfram still do not overcome the inherent weakness in certain geodesic enclosure strut designs caused by crimped or tapered weaker strut edges and a stronger strut mid-section.
Therefore, there is a need for an improved hub and strut system that provides a universal hub assembly that reduces manufacturing costs, improves the strength of geodesic enclosures, and simplifies assembly thereof for various sizes and frequencies. The present invention accomplishes these objectives.